1	Congenital Portosystemic Shunts: Questions and Answers Karen Tobias, DVM, MS Diplomate ACVS Professor, UTCVM
2	What is a portosystemic shunt? A PSS is an abnormal blood vessel that takes blood around the liver instead of through it. Single PSS are birth defects (congenital); multiple PSS are acquired from severe liver disease or high blood pressure
3	How do congenital shunts form? Shunts outside of the liver (extrahepatic) form when the blood vessels hook up abnormally in the fetus
4	How do acquired shunts form? Multiple acquired shunts often form in dogs with severe swelling or scarring of the liver, or dogs that do not have normal microscopic liver vessels.
5	What breeds commonly get congenital shunts? Small breed dogs usually have extrahepatic shunts (abnormal fetal development) Large breed dogs usually have intrahepatic shunts (fetal ductus doesn’t close)
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8	What are the clinical signs of PSS? “Poor doer” Small, less muscle, weak Neurologic abnormalities Quiet, confused, wobbly, drunk, blind, seizures Urinary tract abnormalities Urinates frequently, gets infections from ammonia crystals or stones in the bladder or kidneys Gastrointestinal abnormalities Vomiting or diarrhea No clinical signs in some dogs
9	What affect does the shunt have on blood work? The liver can’t make enough proteins or sugar and can easily become inflamed because it doesn’t have enough nutrition or oxygen Low Blood urea nitrogen (BUN) Low albumin and total protein Low glucose (sugar) High ALT, AST (liver enzymes)
10	What are bile acids? Bile acids are used to digest fat and are emptied into the intestines after eating. They are constantly being reabsorbed and must be filtered by the liver.
11	How are bile acids tested? Your veterinarian will take a fasting blood sample, then feed your dog a meal with fat in it (K/D or L/D diet work well) A second blood sample is taken two hours later, after the gallbladder has contracted because of the fat. This sample is usually higher than the fasting sample.
12	Why do some dogs have higher bile acids after fasting than eating? Some dogs have a normal gallbladder contraction in the middle of the night, and so the fasting sample is higher than the fed sample. This is why 2 samples are taken.
13	What do high bile acids mean? High bile acids mean the liver is not working properly. This can be caused by any liver disease. Dogs with shunts always have high bile acids. Often they are over 100 (normal <10 or 15). Some dogs with shunts have bile acids of 20-25.
14	How can we be sure a dog has a shunt? Definitive diagnosis is based on ultrasound, scintigraphy, portography, CAT scan, MRI, or a surgical exploratory. Definitive diagnosis is NOT based on blood work or liver biopsy. Dogs with portal atresia, hepatic microvascular dysplasia (MVD/HMD), and other medical conditions can have the same blood work and biopsy results as dogs with PSS
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16	What does scintigraphy look like? Rectal scintigraphy does not tell the location or differentiate between single and multiple PSS Splenic scintigraphy can often tell location and and number of shunts
17	Ultrasonography The ability to diagnose a shunt with ultrasound depends on the skill and experience of the veterinarian and the size and cooperativeness of the dog
18	Portography A portogram usually requires surgery to perform. Portograms will tell number, location, and type of shunt
19	What is the medical management for dogs with shunts? Protein restricted diet Lactulose or yogurt +/- Antibiotics For severely ill dogs: Intravenous fluids with dextrose (sugar) Enemas
20	Can I feed a homemade diet to a dog with PSS? Dogs with liver shunts have imbalances of several vitamins and minerals and require specific types of protein and carbohydrates. If you use the homemade diet on our website, you should not vary the ingredients.
21	Are there any supplements that will help liver function? Milk thistle (silymarin) helps the liver grow after surgery and also helps detoxify the blood and improve liver function. Diets or supplements often have zinc and Vitamin E as well. Marin by Nutramax HepatoSupport by Rx Vitamins for Pets Denosyl (Sam-e)?
22	What is the prognosis for dogs that are only treated medically? Over half of these dogs are euthanized an average of 10 months after diagnosis because they get worse or their owners give up One third of the dogs survive at least 5 to 6 years after diagnosis These dogs tend to be older at the time of diagnosis, have blood work that is closer to normal, and have few clinical signs.
23	What surgical treatments are available? Ameroid constrictors Cellophane bands Suture ligation Still being researched: Coils: Penn., Texas A&M Inflatable cuff occluders: U Fla
24	What is an ameroid constrictor?
25	Which surgical technique is best? Any surgery that causes slow constriction (ameroid, cellophane band) is better than rapid constriction (suture ligation). Surgery outcome is also based on the experience of the surgeon and the severity of the dog’s liver disease. Ask the surgeon: How many of these do you perform each year? What is your overall outcome? What is your complication rate? What complications do you see or expect?
26	What is the outcome with Ameroid Constrictors at University of Tennessee? Mortality rate is 1% (compared to 2 to 15%) 85% of dogs are clinically normal within 4 to 6 months (similar to other surgeons) At least 25% of the dogs continue to have high bile acids for the rest of their lives.
27	What complications can occur after surgery? Pain Cold body temperature Low blood sugar Seizures (0% at UTCVM) Shock or swelling from sudden blockage of the shunt
28	What management does a shunt dog need after surgery? Continue the protein restricted diet until liver function improves Lactulose, yogurt, or antibiotics may be recommended for some dogs Recheck bile acids and blood work in 2-3 months Switch to adult maintenance or lite dog food when blood work is normal
29	What if the bile acids are still high after 2-3 months? Continue the protein restricted diet and yogurt Give milk thistle (silymarin) If the bile acids are still high 4-6 months after surgery, a scintigraphy, portogram, and/or liver biopsy may be needed to determine the cause. Yorkies are also predisposed to hepatic microvascular dysplasia and can have both PSS and MVD
30	What is portal atresia or hepatic microvascular dysplasia (HMD or MVD)? The microscopic vessels within the liver are too small Hereditary, especially in Yorkies, Cairns, and Maltese Clinical signs can be non-existant, mild, or severe Diagnosis: Abnormal liver biopsy with normal scintigraphy or portogram. Treatment: Medical management Outcome varies- some dogs live a normal life and some dogs die in months
31	What do we know about shunt genetics? PSS occur in both sexes and can skip generations Yorkies with shunts are more inbred Breeding outside of affected family lines reduces the occurrence of shunts in Irish Wolfhounds Breeding affected Cairn terriers or their offspring produces more shunt puppies Breeding Cairn terriers dogs with MVD can produce shunt puppies
32	What can you do to help? Make sure all breeding dogs have normal bile acids (less than 5 and 10) Do not breed dogs with shunts or parents of dogs with shunts. Siblings? Have all puppies’ bile acids tested at 6-8 weeks Educate other breeders and owners Speak openly about the disease Support rescue associations and research efforts
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